It was the kind of gaffe that could happen at a party conference anywhere from Blackpool to Tampa. At a conclave of the Indian National Congress in January, veteran MP Mani Shankar Aiyar made a joke about the opposition politician Narendra Modi, who is from a low caste and once helped his father sell tea. "There is no way [Modi] can be prime minister in the 21st century," Mr Aiyar reportedly said, "but if he wants to come and distribute tea here we can make some room for him!" By the time the MP denied the remarks, the story was flying around the Indian media as an example of everything that is wrong with the patriarchal Congress party. Mr Modi meanwhile has made hay with the gaffe, playing up his man-in-the-street appeal with a series of tea-based rallies.

Living next door to another coming country, China, means India's arc is often overlooked. Forthcoming elections in the world's largest democracy will, however, be an event of global significance, an awe-inspiring logistical exercise. Voting begins on 7 April and continues for six weeks in nine separate tranches because of the logistical Everest of balloting an electorate of more than 814 million.

Getting a hold on the politics of such a country is no easy task: it has many players and the issues are different in every region, from the northern "Cow Belt" to the deep south. The only certainty is that Manmohan Singh will no longer be prime minister. After two terms in office, the 81-year-old economist is stepping down with a mixed legacy. The workings of his government are opaque – Mr Singh has given just a handful of press conferences in 10 years – but there has been a clear tension between his role and that of Sonia Gandhi, the matriarch of a dynasty that is never far from power. As a result, the party's policies lacked coherence and the economic boom of Mr Singh's first term in office stuttered in his second term. In part this can be blamed on the global crisis, but culpability also rests with Mr Singh's inability to clear away the hurdles that constrain India's economy. Growth has been a fraction of that in China, and has come with high inflation. Much of the wealth generated in the boom years has gathered in the hands of the elite.

Congress will likely plump for Rahul Gandhi as its new prime ministerial candidate. At 43, the scion of Rajiv and Sonia should at least appeal to the young electorate: two-thirds of the population are under 35 and 150 million are eligible to vote for the first time. But while Mr Gandhi bears the gift and burden of the family name, he is inexperienced and, as yet, appears to lack the political touch of his father, the authority of his grandmother, or the legendary status of his great-grandfather.

For these reasons and others, Congress will likely take a pasting. Though polling in such a large country is more alchemy than science, there is a strong possibility that the BJP will form the next government, probably with Mr Modi as prime minister. Mr Modi is one of the most polarising politicians to have walked India's political stage for many years. He is the candidate of change, and has established a reputation as an effective manager, which appeals deeply to voters who spend their lives trying to negotiate bureaucracy. But he has been repeatedly accused (and cleared) of stoking anti-Muslim violence in Gujarat in 2002, in which a thousand or more people were killed. It was only in 2012 that the UK decided to end a boycott of Mr Modi by senior officials. The US has followed suit in recent weeks.

A third force is the new Aam Admi party, which has its roots in a broad anti-corruption movement and has made a point of transparency and accountability. Yet the AAP remains a reaction to India's political woes and not, or at least not yet, a solution for them.

India needs change. It needs reform, infrastructure and jobs for hundreds of millions of young people. The best hope of resisting the nationalist BJP, now or in 2019, lies with Congress, the party that has dominated Indian politics for best part of 70 years. To be able to win over the country, however, Congress must first find the strength to modernise itself.